A Coryneform bacterium is an industrially important aerobic Gram-positive bacterium which has previously been used for producing useful organic compounds such as various amino acids, lactic acid, succinic acid and the like. Particularly, since a Coryneform bacterium has a peculiar metabolism function that a metabolism pathway for producing a substance is not deteriorated even under a condition that cell division is suppressed by a method of restricting oxygen supply or the like, a nutrient source such as saccharides and the like which is given to a Coryneform bacterium is not consumed for proliferation, and is effectively directed to an objective product. Thus, a raw material nutrient source is effectively utilized, and the technique of producing an objective substance can be easily controlled because of suppression of cell division, and this is why a Coryneform bacterium is industrially paid attention.
In order to highly exert such characteristic function of a Coryneform bacterium, it becomes necessary to effectively and highly express various protein genes necessary for producing an objective product, and suppress expression of unnecessary protein genes. For doing this, a technique which can enhance and/or suppress the promoter function associated with these protein genes becomes important.
As to a DNA fragment having the promoter function in a Coryneform bacterium, some DNA fragments are known.
For example, a DNA fragment having a stronger promoter function than the tac promoter derived from Escherichia coli is found out on a chromosome of a Coryneform bacterium, and a DNA sequence thereof is known. And, as a method of controlling expression of the promoter function, a method of changing a carbon source composition of saccharides, ethanol and the like which are added to media has been proposed (see Patent Literature 1).
In addition, a promoter DNA sequence associated with a specified enzyme protein (aspartase) gene expressed in a Coryneform bacterium has been found out (see Patent Literature 2). However, as a method of expressing the promoter function, there is only stated that “when incorporated into a plasmid vector together with a gene encoding a protein, and is introduced into a host Coryneform bacterium, an action of potentiating an expression intensity of the gene is possessed”, and nothing is referred to a method of enhancing, and a method of controlling expression of the promoter function.
In addition, a promoter or promoters of exogenous and endogenous genes involved in production of L-glutamic acid and L-lysine which functions in a Coryneform bacterium is found out (see Patent Literature 3), but nothing is referred to a method of enhancing expression of those functions.
A technique of using a Coryneform bacterium in which the function of a promoter of a dapA gene (dihydrodipicolinic acid synthase gene) has been enhanced by a mutagenesis method, in production of L-lysine has been proposed (see Patent Literature 4). However, nothing is referred to the function enhancement under an anaerobic condition.
Regarding a method of inductively-expressing the promoter function, a recombinant DNA sequence containing a pfl (pyruvate formate lyase gene) promoter which is induced by pyruvic acid and suppressed by oxygen (Patent Literature 5), and a promoter responsive to a stress such as an oxidative stress (addition of peroxidated lipid), an osmotic stress and a glucose starvation stress of a 2-deoxyglucose-6-phosphate dephosphorylase gene of yeast Saccharomyces cerevisiae (Patent Literature 6) are also known. Patent Literature 6 refers to chemical inducing methods such as a phosphoric acid-deficient inducing method, a copper addition inducing method and the like, a heat shock inducing method, and the like as methods of inducing various gene promoters in addition to the aforementioned ones.
As described above, DNA sequences of various promoters, and methods of inductively-expressing the promoter function with various drugs or stresses are known, but a method of controlling the promoter function which functions in a Coryneform bacterium, which is inductively-enhanced and/or inductively-suppressed in a reaction medium under an anaerobic condition, and a DNA fragment having the promoter function of the present invention are not known.    Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 7-95891    Patent Literature 2: JP-A No. 7-31478    Patent Literature 3: International Publication WO No. 95/23224    Patent Literature 4: JP-A No. 2001-61485    Patent Literature 5: JP-A No. 3-80088    Patent Literature 6: JP-A No. 2000-78977